New protein gel regenerates tooth enamel — revolutionizing dental health

A cracked tooth or loss of enamel can make you feel vulnerable every time you sip on something cold or bite down a bit hard. Most people learn to live with that sharp pain or the anticipation of more damage to come.

For decades, a lot of dentists could only slow the problem down. Once enamel is gone, it doesn't come back. New research now suggests, though, that your teeth may someday regenerate, with some help from a material that imitates nature's original blueprint.

Enamel protects every tooth against the forces of chewing, acids, hot drinks, and years of wear. It forms when specific proteins direct tiny mineral crystals into long, organized structures. Those structures can be tightly arranged and resist breaking. After childhood, the body ceases to produce these proteins, which is why enamel cannot regenerate on its own.

Researchers studying this process contemplated a natural protein called amelogenin. Amelogenin forms loose strands through a gathering of calcium ions during development that help direct the crystals to grow appropriately. From there, researchers set out to imitate that early environment, hoping that damaged enamel could again recover some of its structure.

The team working in this capacity created a protein-based substance called an elastin-like recombinamer. These small engineered molecules fold and build into thin fibers when mixed with calcium and thoroughly dried out. The fibers, which are about 15 to 40 nanometers wide, create a type of scaffold with numerous tiny places where mineralization can begin.

Using high-resolution imaging in their tests, researchers found that the fibers maintained the same spacing observed in natural enamel-forming proteins. This arrangement plays an essential role in directing new minerals for growth. In their experiment, the researchers applied the fibers to tooth surfaces and then added a liquid that was enriched with calcium, phosphate, and a small amount of fluoride to initiate mineral crystal formation.

Within two hours, mineral crystals had started to form, appearing initially as soft platelets. By the end of the next day, the crystals had matured to long, needle-shaped fluorapatite crystals extending about one micrometer in length.

The new crystals grew in alignment with the original protein fibers, which is significant. The strength of real enamel derives from crystals that grow long, organized, and aligned. The researchers then placed small hydroxyapatite nanoparticles under the fiber coating, and upon observation, the newly formed crystals aligned again in the same unified orientation as the existing crystals. This indicates that protein matrices can rebuild enamel in situ and support the growth of new mineral directly on top of existing, older tooth tissue.

Next, the team wanted to test their approach on real human tooth samples. They began to work with prismatic enamel, which makes up the majority of the tooth's surface, as well as aprismatic enamel and exposed dentine. The team then etched the surfaces lightly, applied a thin coat of the protein material, and immersed the samples in the mineral solution.

On prismatic enamel, the regenerated layer emulated the natural enamel prism configuration and displayed spaces in between. Mechanical testing indicated that the regenerated surface obtained stiffness, hardness, and wear resistance comparable to healthy enamel.

On dentine that typically gets exposed when enamel wears, the coating produced an enamel-like layer, possessing a significant amount of stiffness with decreased frictional resistances and thus lessening sensitivity and enhancing bonding with dental restorations. The rebuilt layer exhibited stiffness of about 58 gigapascals (GPa) and hardness of 1.4 GPa - values that approached the natural states.

Durability in real-world conditions is a fundamental question for any dental repair. The regenerated layer was analyzed in hostile environments: acidic solutions, alkaline solutions, high salt, extended brushing, and in temperatures of heat or cold, and also in ultrasound conditions.

The surface remained stable, intact, and continued to mineralize. Mechanical durability, as compared to a common dental varnish, showed that the newly produced material demonstrated mechanical durability in the same range and, in certain instances, better.

Dentists can apply the material in several minutes of appointment time and do not require heat or complex tools. It dries quickly and then draws minerals from the surrounding solution or saliva. Its ease of use could facilitate integration into routine management.

Researchers at the University of Nottingham also created a gel derived from proteins that would guide enamel growth similarly. The gel is fluoride-free and can lie on the tooth surface like traditional treatments. Ultimately, a thin layer is created to fill the little holes and cracks and mimics free calcium and phosphate from saliva to rebuild minerals in an organized manner.

Lead author Dr. Abshar Hasan said they found that the regenerated enamel acted just like the real enamel subjected to brushing, chewing, and acid exposure. Additionally, this gel could be placed on dentine, alleviate sensitivity, and restore bonding. Study lead Professor Alvaro Mata said that their aim was to develop a product that is easily placed in the dental office treatment flow. A start-up, Mintech-Bio, has begun a process for bringing the advances to patients.

Both paths have a lot of promise, but researchers have cautioned that studies in the actual mouth have not yet been addressed. The mouth is dynamic, constantly bathed in bacteria, saliva, changing temperatures, and relentless chewing forces. These considerations may impact the longevity of bonding and efficacy.

However, for anyone who has been told by a dentist to the effect that once enamel is lost, it is gone, this work leads to a new anticipated life. After more studies, these materials could have a future to help rebuild something permanent, in a way, with something new.

Research findings are available online in the journal Nature Communications.

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